package com.xinpu.shiro;


import com.fasterxml.jackson.databind.ObjectMapper;
import com.xinpu.exception.AuthException;
import com.xinpu.vo.ResponseMessage;
import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;

/**
 * 执行流程 preHandle -> isAccessAllowed ->isLoginAttempt ->executeLogin
 */
public class JWTFilter extends BasicHttpAuthenticationFilter {

    /**
     * 认证名称
     */
    private final String AUTHORIZATION_NAME = "Authorization";

    /**
     * 这里我们详细说明下为什么最终返回的都是true，即允许访问
     * 例如我们提供一个地址 GET /article
     * 登入用户和游客看到的内容是不同的
     * 如果在这里返回了false，请求会被直接拦截，用户看不到任何东西
     * 所以我们在这里返回true，Controller中可以通过 subject.isAuthenticated() 来判断用户是否登入
     * 如果有些资源只有登入用户才能访问，我们只需要在方法上面加上 @RequiresAuthentication 注解即可
     * 但是这样做有一个缺点，就是不能够对GET,POST等请求进行分别过滤鉴权(因为我们重写了官方的方法)，但实际上对应用影响不大
     */
    @Override
    protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
        // 判断用户是否想要登入
        if (this.isLoginAttempt(request, response)) {
            try {
                // 进行Shiro的登录UserRealm
                this.executeLogin(request, response);
            } catch (Exception e) {
                // 认证出现异常，传递错误信息msg
                String msg = e.getMessage();
                /**
                 * 错误两种处理方式
                 * 1. 将非法请求转发到/401的Controller处理，抛出自定义无权访问异常被全局捕捉再返回Response信息
                 * 2. 无需转发，直接返回Response信息
                 * 一般使用第二种(更方便)
                 */
                // 直接返回Response信息
                this.responseException(request, response, msg);
                return false;
            }
        }
        return true;
    }

    /**
     * 无需转发，直接返回Response信息
     */
    private void responseException(ServletRequest req, ServletResponse resp, String msg) {
        HttpServletResponse httpServletResponse = (HttpServletResponse) resp;
        httpServletResponse.setStatus(200);
        httpServletResponse.setCharacterEncoding("UTF-8");
        httpServletResponse.setContentType("application/utils; charset=utf-8");
        PrintWriter out = null;
        try {
            out = httpServletResponse.getWriter();

            ObjectMapper mapper = new ObjectMapper();
            String data = mapper.writeValueAsString(ResponseMessage.unautho(msg));
            out.append(data);
        } catch (Exception e) {
            // throw new CustomException("直接返回Response信息出现IOException异常");
        } finally {
            if (out != null) {
                out.close();
            }
        }
    }

    /**
     * 检测Header里面是否包含Authorization字段，有就进行Token登录认证授权
     */
    @Override
    protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
        // 拿到当前Header中Authorization的AccessToken(Shiro中getAuthzHeader方法已经实现)
        return true;  //保证一直验证登录
    }


    /**
     * 执行登录
     *
     * @param request
     * @param response
     * @return
     * @throws Exception
     */
    @Override
    protected boolean executeLogin(ServletRequest request, ServletResponse response) {

        HttpServletRequest httpServletRequest = (HttpServletRequest) request;

        String authorization = httpServletRequest.getHeader(AUTHORIZATION_NAME);
        if (authorization == null) {
            throw new AuthException("您没有权限访问");
        }
        JWTToken token = new JWTToken(authorization);
        //提交token最shiro处理
        getSubject(request, response).login(token);
        return true;
    }

    /**
     * 跨域支持
     *
     * @param request
     * @param response
     * @return
     * @throws Exception
     */
    @Override
    protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {

        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        HttpServletResponse httpServletResponse = (HttpServletResponse) response;
        httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
        httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,PUT,DELETE,OPTIONS");
        httpServletResponse.setHeader("Access-Control-Allow-Headers", httpServletRequest.getHeader("Access-Control-Request-Headers"));
        httpServletResponse.setHeader("Access-Control-Expose-Headers", "Content-Disposition");
        // 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
        if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
            httpServletResponse.setStatus(HttpStatus.OK.value());
            return false;
        }
        return super.preHandle(request, response);
    }
}
